This invention relates generally to fluid mixing, and more particularly, to a method and apparatus for mixing dissimilar liquids and dissimilar fluids such as a gas and a liquid or dissimilar liquids; and specifically to those devices wherein rotating elements are employed to mix the fluid passing through them. Although there are numerous applications requiring mixing apparatus, one such application is for the clarification of waste water, where the waste water and air are to be mixed together in order that the pollutants carried in the waste water can be broken down through being decomposed by oxidation. Conventional mixing apparatus usually employ some form of shaft-driven impeller arrangement located within a chamber in which the fluids are introduced. Such apparatus, however, often provides a poor quality product mix and are therefore not always the best solution for an intended application. Other types employ rotating drums or rotors, where the fluids, initially brought together external of the apparatus, are then directed to navigate past a relatively small annular clearance between the outer static housing and the inner rotating drum where there is sufficient flow turbulence to refine the mixture or to thoroughly oxidize the pollutants carried in the mixture.
Such an example of mixing apparatus is shown in U.S. Pat. No. 6,627,784 where the two dissimilar fluids are combined together at a single pipe junction external of the machine, and distributed via two pipes to respective inlets at opposite ends of the machine. While some superficial mixing of the fluids will undoubtedly occur as they are introduced into a single pipe, the concentrated mixing occurs only as the fluids have been distributed to enter from both ends the annular clearance between rotor and housing before exiting the machine at the midway point. The rotor, by being provided with surface irregularities on its exterior generates cavitation in the liquid passing through the unit resulting in a better mixing than would be normally possible with a smooth rotor. The phenomena of cavitation is normally an occurrence best avoided in the operation of machinery, but for producing a good mixture between of fluids of dissimilar type, there are definite advantages for having such phenomena take place during operation of the machinery.
Even so, for certain applications and choice of fluids as well as such issues as when dealing with waste water, there would be an advantage if respective fluids could be first brought together in the interior of the housing rather than externally of the machine as taught by U.S. Pat. No. 6,627,784. The resulting pipe work on the input side would be simpler to install and maintain as each fluid input would have it own separate pipe connected directly to the housing. Furthermore, there would be advantage in the promotion of more effective mixing of the fluids if a majority of the exterior surface length of the rotor could be used rather than the comparable shorter distance available on the rotor of U.S. Pat. No. 6,627,784. By effectively doubling the travel distance of the fluids, a better mix is possible. There would also be an additional advantage in a device where the separate intakes for the dissimilar fluids entering into the working clearance between rotor and housing would in be quite close together, preferably arranged in a manner to lessen any likelihood of reverse flow. Reverse flow can trouble the rotor shown in U.S. Pat. No. 6,627,784, as here the fluids are entering at both ends of the annular clearance between rotor and housing and may not flow in equal measure, for instance, should there be a significant variation in the pressure drop between the two input circuits, a resulting disproportionate quantity of fluid would flow to that side where the resistance to flow is less.
There therefore is a need for a new solution for an improved fluid mixing device, and preferably where the separate fluids can be introduced to the device quite independently, and where mixing of the fluids can occur on or about the rotor surface, and where there is less likelihood for the fluid to flow in a reverse direction to that desired. For instance, were the dissimilar fluids entering the chamber of such a device separated by at least one array of surface irregularities disposed over a relatively short lengthwise distance on the surface of the rotor, an additional disturbance to the flow path of the fluids could mitigate against reverse flow conditions as one of the two fluids would first to have to traverse this distance before reaching the second fluid. In essence, the first fluid, by being subjected to the influence of cavitational disturbance induced by this initial array of surface irregularities during its transit towards meeting the second fluid, is thought to increase the general turbulence in the first fluid such that it has a greater impact once it makes contact with the second fluid. The resulting impact between the fluids, being more vigorous than would otherwise occur, when two fluids carried by separate pipes are merged, creates greater turbulence and helps in the creation of better overall fluid mix, particularly when further arrays of surface irregularities are disposed along the remaining rotor surface in the direction towards the fluid exit.
The present invention seeks to alleviate or overcome some or all of the above mentioned disadvantages of earlier machines. The device comprising few working parts and relatively simple to implement, thereby minimizing the possibility of component failure and avoiding expensive and time-consuming machine downtime, offers better regulation of the fluids entering the device to ensure a better quality of mixture of the fluid exiting the device.